Shield for magnetic coils.



SHIELD FOR MAGNETIC COILS.

APPLICATION FILED SEPf. I1. I9I1.

1,251,700. Patented Jan. 1, 1918.

I I. [NVENTOR 7720mm Shaw- ATTORNEY UNITED STATES PATENT OFFICE.

THOMAS SHAW, OF HACKENSACK, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONI AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

SHIELD FOR MAGNETIC COILS.

Patented Jan. 1, 1918.

Application filed September 17, 1917. Serial No. 191,776.

and State of New Jersey, have invented cermaterial ener with-a ring core formed of two sections 1 tain Improvements in Shields for Magnetic Coils, of which the following is a specification.

My invention relates to improvements in the construction of ma etic coils, more particularly coils of the ring type used in tele hone work as loading coils and the like.

uch coils are usually constructed with a core inthe form of a magnetic ring made up of a bundle of wires or laminations upon which the coil is wound. In order that the coil shall be self restoring with res ect to its impedance constantsefter being subjected to the effect of magnetizing currents, the core is made discontinuous by the provision of an air gap, whereby a demagnetizing action occurs at the core pole faces of the air gap,

tending to restore the core to normal conditions.

Since coils of this character are usually mounted in containing cases of cast iron or other metal, the above construction results in losses when the stra netic field of t e air gap intersects t e casing. It is the purpose of the present invention to reduce these losses by surrounding the coil, at least in the vicinity of the air gap by a shield of finely laminated iron,

the lamiuations extending parallel with the 0 core. In order to reduce the losses as much as possible the iron material constituting the shieldshould have a highspecific resistance and low permeability. Leakage losses due to hysteresis may be kept low by using a material which has low 11 steresisunder the saturation conditions pro need by the leakage field from the air gaps. These and other objects of the invention mav be attained by means of the construction illustrated in the. accompanying drawing, Figure 1 of which is a diagrammatic representation of a coil constructed in accordance with the invention, Fig. 2 being a section taken on line a-a of Fig. 2, Fig. 3 being a broken view showing in more detail the construction of the magnetic shield, and Fig. 4 being a broken view of a modification.

Referring to l the coil is provided and 2, each section being made up of a bundle of wires or the like 3 in a manner mag-- the shield thus formed lie as shown. The winding 5 is siown heavier than winding 6 in; the diagrams merel to readily distinguish between the turns 0 the two windings, it being understoodthat the windings may be of the same or difl'erent kinds of wire and of va g number of turns, depending upon the esign of the rticular coil. In orderto reduce the lea age losses due to stray magnetic fields intersectmg the containing casin (not shown) of the coil a magnetic shield l is provided, said shield being arranged so as to surround the anterior of the coil winding at least in the vicinity of the air gaps as shown in Fi L Said shield may if desired be constructed as indicated in greater detail in Fig. 3, hy applying a plurality of parallel core wires 8 to .a strip or sheet of fabric 9 such as heavy paper, cloth or the like by means of a bindmg material such as shellac. The strip is ,then wound about the exterior of the coil in such manner that the parallel wires of parallel to the core ires. If desired the shield may be arran ed upon the interior of the coil and upon the outer surface of the co to the air gaps as shown at 10 in ig. 4.

By the above ascribed constructions the air gap is brid by elements of laminated magnetic material, thereby decreasing the losses due to stray magnetic fields in the vicinity of the air gaps. Other constructions than those illustrated may be utilized to accomplish the desired results without departing from the s irit of the invention and it will therefore understood that all such structures as fall within the scope of the appended claims are to be considered as within the purview of the invention.

What is claimed is:

ad acent 1. A magnetic coil, having a discontinuous tinuities thereof comprising a-shield formed of magnetgiglemcnts separated by non-mugnetie spaces.

4. A magnetic coil haying a. discontinuous core, and means for bridging discontinuous portions thereof comprising a. shield formed of laminated strips parallel to the core."

5. A magnetic coil having a discontinuous core an d means for bridging the ga 's or discontinuit es therein comprising a shield ar, ranged externally of the coil and consisting at least input of magnetic 'materiaL extending m-a direction 6, .A magnetic coil'having n discontinuous. cure, end-menus for bridg n the gaps con- .stitntmg the discontinuities ereof comprising a. shield -soidj shield being formed of parhllelihimmetions and surrounding the .in;; the self-demu core in such manner that. the lnmmauun r tend in a direction parallel. to the core.

7. A magnetic coil having :1 core of n'mgnetic materiah-n gap in 5' id \016 to render said core self-(lenmgnetizingso that the impedance constants of the coil will readil' return to their normal value after the coil has been subjected to tilteflect of magnetizing current, and means to reduce the reluctance of the gap without materially reducetizing elfeet of the core comprising a. shie d formed at least in art of magnetic material and arranged :1. out the cone.

In testimony whereof, I have signed-my name to this specification this eleventh clay THOMAS SHAW.

' of September 1917. 

